Recently, in order to reduce a wire length so as to promote a high speed of a device, a technique stacking a plurality of semiconductor chips in a thickness direction (referred to as, for example, a 3D-LSI) has been proposed. In order to electrically connect the semiconductor chips stacked in the thickness direction, a through electrode that passes through a silicon wafer forming the semiconductor chip in the thickness direction is formed and is called as a through-Si via (TSV). See, for example, Japanese Patent Application Laid-Open No. 2010-103195.
The formation of the TSV includes an etching process of forming a bottomed hole (for example, a hole having a diameter of about 10 μm and a depth of about 100 μm) on the silicon wafer by dry etching, such as for example, reactive ion etching (RIE) and an embedding process where a conductor is embedded in the hole. A film-forming process of forming a thin film such as an insulating film, a barrier film, and a seed film on at least the inner side of the hole is performed between the etching process and the embedding process as necessary. If the hole is formed by the dry etching, a residue such as polymer is attached to the inner side of the hole. The residue having a bad influence on the subsequent embedding process and the film-forming process as the previous process, needs to be completely removed.
In order to remove the residue, a cleaning processing is performed using the chemical liquid. Because the hole for the TSV has a very large aspect ratio (hole depth/hole diameter), the chemical liquid hardly penetrates into the hole. Although the chemical liquid may penetrate into the hole a prolonged time has elapsed, it is not desirable because the productivity of the semiconductor device is deteriorated. In some cases, even though the etching rate is low, the chemical liquid for removing the residue may etch other useful films formed in advance such as the insulating film that covers the entire surface of the wafer. From this viewpoint, the chemical liquid processing may not be performed for a long time. Such problem is not limited to the formation of the TSV, and similarly exists even in processing of a substrate having a minute concave portion (for example, holes and trenches), particularly, a minute concave portion having a high aspect ratio.